Non-fault Detection before Reclosing Using Parameter Identification for Medium Voltage Distribution Lines

Aiming at the problem of blind reclosing of permanent faults for three-phase tripping of phase faults in medium voltage distribution lines, this paper proposes a proactive non-fault discrimination method based on the principle of parameter identification before phase reclosing in distribution networks. Line phase-to-phase fault three-phase tripping, three-phase symmetrical low-frequency voltage excitation is applied to the line, three-phase symmetrical and each equal-value network for the line equivalent resistance, inductance linear composition; In the case of permanent faults, the three-phase asymmetrical and fault-equivalent value network is related to the transition resistance and fault location, which cannot be characterised as a linear relationship between resistance and inductance, and the difference is used for phase-to-phase non-fault identification. Taking the non-fault network as the identification benchmark model, the least squares algorithm is used to identify the resistance and inductance parameters to establish the nonfault identification criteria, and when the calculated values of the resistance and inductance are consistent with the actual values, then the actual model is consistent with the benchmark model, and it is judged to be non-fault. Simulation results show that the nofault criterion before reclosing proposed in this paper is able to reliably identify the fault nature under different fault locations and transition resistances.